Chemical Potential Energy

Discussion

introduction

Calorimetry and so on.

Q = mcΔT

Burn a sample of the substance in oxygen, use the heat given off to warm a bit of water and watch the temperature rise.

When comparing substances, it's often more instructive to speak of their specific energy or specific work or gravimetric energy density or volumetric energy density (energy per mass) symbol e or w.

e =  E
m

or energy density (energy per volume) symbol u or η (eta) or ε (epsilon).

u =  E
V

rather than their energy.

simple compounds specific energy
(MJ/kg)
fossil fuels specific energy
(MJ/kg)
carbon (to CO2) 32.8 coal, anthracite > 32.6
carbon (to CO) 22.7 coal, bituminous 24.4–32.6
ethanol 29.7 coal, sub-bituminous 19.3–24.4
hydrogen 142 coal, lignite 14.7–19.3
methane 55.5 diesel 45.3
methanol 22.7 gasoline, automotive 45.8
nitromethane 11.6 gasoline, aviation 43.1
octane 47.9 jet a 43.3
propane 50.3 jet b 43.5
sulfur 9.16 kerosene 46.3
foods specific energy
(MJ/kg)
oil, crude (petroleum) 41.9
oil, heating 42.5
carbohydrates 17.2 biomass fuels energy density
(MJ/kg)
fats 38.9
proteins 17.2 alfalfa straw 18.4
explosives specific energy
(MJ/kg)
charcoal 29.0
coconut husks 9.8
ANFO 6.3 coconut shells 17.9
BTTN   coffee husks 16.0
C4 6.3 cotton hulls 19.4
composition b   cotton stalks 17.4
composition c   dung, air dry 12.0
dynamite 7.5 groundnut shells 19.7
gunpowder 3.0 maize cobs 18.9
HMX   maize stalks 18.2
lead azide   peat 14.6
nitrocellulose   rice hulls 15.5
nitroglycerine 6.4 rice straw 15.2
PETN 5.8 sugar cane bagasse 19.0
RDX   sorghum bagasse 18.9
semtex   soybean stalks 19.4
silver azide   wheat straw 18.9
silver nitride 0.9 wood, green 10.9
sodium azide   wood, air dry 15.5
TATP   wood, oven dry 20.0
torpex 7.0    
TNT 4.7    
Specific energy of selected substances

fuel

A word about fuel based units.